Abstract: Despite of the wide use of hydroxyapatite (HA) for bone repair and regeneration, its
brittleness has limited clinical application to less stressed body parts. Thus, evaluation of HA
mechanical properties has been an important research matter. The aim of this study is to assess the
compressive strength of a stoichiometric HA with 1.66 Ca/P molar ratio, synthesized by
hydrothermal method. Cylindrical samples were processed by uniaxial compacting, followed by
sintering. Compressive strength of cylindrical samples with 2.0 medium diameter/height ratio was
measured according to ASTM C 1424. Load to failure divided by the cross-sectional area of the
samples were reported and microstructural characterization was made by MEV-EDS. The
compression strength results were compared to values reported in the literature.

Abstract: The aim of this study was to evaluate the osteoconductive properties of synthetic porous hydroxyapatite prepared by low-temperature microwave processing OssaBase® HA (SPHA) in comparison with biological apatite, non-sintered deproteinized bovine bone Bio-Oss® (DBB). The materials were implanted into the bone sockets of the tibia of Beagle dogs for 3 and 6 months. The bone response to granules of the materials of similar sizes was compared. Histological analysis of the specimens with histomorphometry was performed at different times after in vivo implantation. Based on the histological analysis, the level of bone formation in the spaces between the implanted granules and through the interconnected pores of both implanted materials within a cortical region was significantly higher (bone area ingrowth 72–85%) than within a cancellous bone site (bone area ingrowth 16–28%) at three and six months after implantation. According to our study, the bioactive and osteoconductive properties (bone implant contact and bone area ingrown) of the synthetic porous hydroxyapatite are very high and comparable with the biological apatite, non-sintered deproteinized bovine bone. The favourable influence of the high specific surface area and carbonate content of the synthetic, porous hydroxyapatite on bone formation was confirmed.

Abstract: The present work is on the synthesis of forsterite (Mg2SiO4) powder using talc and magnesium oxide powders as the starting materials followed by a heat treatment process. Sintering behavior and mechanical properties of the forsterite bodies were evaluated from 1200°C to 1500°C. Forsterite phase were detected in samples without any secondary phases at all sintering temperatures. A very high fracture toughness of 4.9MPa.m1/2 and Vickers hardness of 7.1GPa were measured for samples sintered at 1400°C, thus indicating the viability of this ceramic for biomedical application.

Abstract: To evaluate the osteoconductive potential of connected porous hydroxyapatite (HAp), we histologically analyzed the newly formed bone inside unidirectional porous HAp (Regenos®, Kuraray, Japan; 75% porosity, n=17) and interconnected porous HAp (Neobone®, Covalent Materials, Japan; 75% porosity, n=10) 26 weeks after their implantation as bone spacers between the split lumbar laminae of goats. As a control, non-connected porous HAp spacers (Apaceram®, Pentax, Japan; 50% porosity, n=5) were used. After staining non-decalcified samples with Villanueva Goldner, changes in pore shape were evaluated microscopically and new bone formation in HAp spacers was quantitatively analyzed. In addition, blood vessel distribution was evaluated by hematoxylin and eosin staining. Changes in pore shape were observed in 76% of the Regenos® spacers and 90% of the Neobone® spacers but were not detected in the Apaceram® spacers. Only limited new bone formation was observed in the Regenos® and Neobone® spacers, whereas vascular-like structures were detected in 82% of the Regenos®, 70% of the Neobone®, and 80% of the Apaceram® spacers. The changes in pore shape were thought to have resulted from the low initial compression strength of the connected porous HAp, which may have limited the inherent osteoconductive potential of connected HAp. Our findings suggest that the maintenance of pore shape is required for promoting new bone formation in connected porous HAp when used as lamina spacers in spinal surgery.